Journal of Geosciences, 56 (2011), 299–316

DOI: 10.3190/jgeosci.102

Original paper

Geology, mineralogy and possible origin of the copper mineralizationin marble near Saldán, Córdoba (Argentina)
Fernando Colombo1*, Raúl Lira2, Edward M. Ripley3, José González del Tánago4
CONICET, Cátedra de Geología General, Facultad de Ciencias Exactas, Físicas y Naturales – Universidad Nacional de Córdoba,
Av. Vélez Sarsfield 1611 (X5016GCA) Córdoba, Argentina; fosfatos@yahoo.com.ar
2
CONICET, Museo de Mineralogía. Facultad de Ciencias Exactas, Físicas y Naturales – Universidad Nacional de Córdoba, Av. Vélez
Sarsfield 299 (5000), Córdoba, Argentina
3
Department of Geological Sciences, Indiana University, 1005 East Tenth Street, Bloomington, IN 47405, USA
4
Departamento de Petrología y Geoquímica, Facultad de Ciencias Geológicas, Universidad Complutense, 28040 Madrid, Spain*
Corresponding author
1

Copper minerals (chrysocolla >> dioptase >> plancheite > tenorite) plus barite and quartz occur in a small lens of granulite-grade calcite–dolomite marble near Saldán, Córdoba Province (central Argentina, 31º18′50.7″S, 64º19′50.0″W).
The mineralization is hosted in fractures (striking N30ºE and dipping 78ºW) that were widened by dissolution.
Chrysocolla mainly fills fractures. It has variable H2O contents but the Cu:Si ratio is always close to 1 : 1. Plancheite
forms compact fissure fillings and aggregates of interlocking spherules. Copper is partially replaced by Mg (up to 2.22
wt. % MgO), with small amounts of Na, K, Ca, Al and Fe also present. Dioptase occurs as prismatic crystals dominatedby {101̄0} and {112̄1} that can reach over 2 cm in length, and also as granular fracture fillings. Unit-cell parameters
are a 14.5719(6), c 7.7799(3) Å, V 1430.7(1) Å3; refractive indices are ε = 1.707(3), ω = 1.656(3), with an anomalous
small 2V. Magnesium (up to 0.15 wt. % MgO) is the only significant substituent. Yellow barite crystals tabular on {001}contain traces of Sr. Quartz occurs rarely, as drusy linings. A few cases of botryoidal, opal-like quartz crusts are known.
Tenorite forms dark brown masses and stringers included in marble. Very scarce grains of copper sulfides (anilite altering
to spionkopite and covellite along rims and cracks) are found scattered in the marble. Copper is partially replaced by Bi(≤ 0.15 wt. % Bi) and Pb (≤ 0.16 wt. % Pb). Malachite and brochantite are alteration products of sulfides.
Fluid inclusion studies indicate that the minerals precipitated from a single-phase fluid initially at a temperature above
300 ºC that cooled to c. 220 ºC. Salinity was very low, 0 to 2 wt. % NaCl eq. Isotopic analyses of calcite give δ13C valuesof 0.4–0.9 ‰ PDB and δ18O values of 17.1–15.1 ‰ VSMOW, coincident with the isotopic signature of the regional
marbles. Calculated values of δ18O for water in isotopic equilibrium with calcite fall into with the Metamorphic Water
Box. The δ34S values of barite are 3.6–4.6 ‰ CDT.
The mineralization possibly precipitated from fluids of meteoric origin that suffered an oxygen isotope shift due to avery low water/rock ratio. The sulfur source could have been sedimentary or igneous sulfides, or a mixture from two
different sources (such as heavy seawater-derived sulfur and light sedimentary sulfides), but not exclusively seawater.
Copper was probably scavenged from accessory sulfides scattered in barren marble or orthoamphibolite. The heat source
remains unknown.
Keywords: dioptase, chrysocolla, plancheite, meteoric fluid, stable isotopes, fluid inclusions
Received: 13 May 2011; accepted: 27 September 2011; handling editor: S. Mills

1. Introduction
The interplay of processes acting on an oxidizing orebody
can produce a vast array of secondary species, depending
mostly on chemical factors such as pH, Eh and availability and activity of cations and anions in the solutions.
Where copper is present in the primary minerals (usuallysulfides), malachite and azurite are the most common
secondary Cu-minerals. However, hydroxy-chlorides, sulfates, arsenates, phosphates, vanadates and silicates may
be locally common and even of economic importance.
Dioptase, ideally Cu6(Si6O18)∙6H2O, is a cyclosilicate
originally discovered in Altyn-Tyube (Altyn-Tube)

deposit, Kirghiz Steppes, Karagandy Province, central
Kazakhstan. René Hauy (1798) first realized that the
crystals considered emerald were in fact a different
species. Even though it is compositionally similar tochrysocolla, dioptase is much scarcer, indicating that theconditions leading to its precipitation are more restricted.
Notably, in a number of the localities where dioptase
is relatively abundant and where it forms the largest
crystals, it occurs associated to dolomite (± calcite) (e.g.
Markham 1959; Cook 2003; Walstrom 2006), suggesting that carbonate-rich environments are favorable fordioptase crystallization. In addition to the type locality,
the most famous finds of this type were made in Africa,
www.jgeosci.org

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

especially at the Tsumeb mine in Namibia (Cook 2002;
Cook and Nicolson 2002). As noted by these authors,
species directly associated to dioptase tend to be few,
even in deposits well-known for their mineralogical diversity; other Cu silicates (chrysocolla and plancheite),carbonates (malachite, calcite, dolomite and azurite) andquartz are among the most frequent. Pseudomorphs ofplancheite after dioptase were also reported (Williams
1962; Vochten et al. 2005).
An occurrence of Cu-bearing minerals is found in marble near the town of Dumesnil, Córdoba Province (central
Argentina). In spite of being volumetrically very small,this locality produced some fine crystals of dioptase. We
a

a

64° W

present here a description of the geology and mineralogy,
complemented by fluid inclusion and stable isotope data,
to infer the origin of this mineralization.

2. Location and historical background
The occurrence is located in an area known as Mal Paso,
between the towns of Dumesnil and Saldán (but closer tothe second one), in Colón Department, Córdoba Province,
central Argentina (31º18′50.7″S, 64º19′50.0″W) (Fig. 1).
Extensive marble mining for use in the cement industry has formerly taken place in this area. Nowadays ac

31.3° S

Córdoba64° W
Deán Funes

queci

65° W

Serrezuela
Cruz del Eje

N
32° S

e Comechingon
es

32° S

33° S

0

20

Sierra d

Atos
Pampa

40 km 65° W

Sierra de
Los Cóndores

Cañadade Álvarez
Sierra de
Las Peñas
33° S
Pampean Rangesof Córdoba
64° W

District with copper mineralizationin marble

La Estanzue

Sierras Chicas

o

och

de P

Sierras Grandes

ra

Sier
Chancaní

Suquía River
SaldánDumesnilCórdobala Fault

Jesús
María 31° S

31° S

N

Dumesnil

El Di

b

to Fa

ult

32° S

2 km

0

64.3° W
References
Unconsolidated sediments
Continental conglomerate and sandstone
Loma Ancha granite
Mylonites (ductile shear zone)
Gneiss and schist
Cordierite diatexite

La Calera Group

Orthopyroxene metabasite
Tonalitic orthogneiss

El Diquecito Group

Amphibolite and marble (M >A)
Copper mineralization

Fig. 1a Position of the Córdoba Province in Argentina (left) and Ranges (Sierras) of Córdoba (black) in the Córdoba Province (right). b – Sketchof the Ranges of Córdoba, showing two districts with copper mineralization in marble. c – Geological map of the studied area.

300

Copper mineralization in marble, Córdoba, Argentina

renewed interest in crushed stone for building purposes
has led to reactivation of some old quarries and openingof new operations that exploit amphibolite and gneiss.
The first report of dioptase from the quarry of “MalPaso” was made by Olsacher (1938), who mentioned that
it was found as aggregates of anhedral (rarely euhedral)
crystals in marble, up to 5 mm long and 1 mm wide.
Gay et al. (1975) mentioned in a footnote that the copper
seams [verbatim] in Mal Paso are ‘very well known for
the existence of dioptase’. Using X-ray diffraction, they
identified plancheite. The next reference to dioptase wasmade by Angelelli et al. (1983), who presented a chemical analysis and a crystal drawing. Finally, Poklepovic etal. (2001) wrote a summary of the occurrence and gavedata about fluid inclusions in dioptase.
After its discovery, this quarry has been owned successively by several individuals, who exploited it intermittently for dioptase specimens. For a period of time thequarry was given the name Esperanza (Hope). Mining
progressed from two opposite sides, leaving an increasingly thinner wall between the two fronts. Most of themining has been made in a rather primitive fashion, withpicks and barrels.

3. Experimental techniques
X-ray powder diffraction patterns (XRPDP) were measured with a PANalytical X‘Pert Pro diffractometer using
CuKα radiation obtained at 40 kV and 40 mA. Unit-celldimensions were refined by full-profile fitting using the
Le Bail method (Le Bail et al. 1988) as implemented by
FullProf 2008 software (Roisnel and Rodríguez-Carvajal
2001). Reported standard deviations have already been
multiplied by a correction factor (SCOR) to compensate
for serial correlation (Bérar and Lennan 1991).
Whole-rock chemical analyses were performed using X-ray fluorescence (Rigaku RIX2000 spectrometer,
wavelength-dispersive mode, Rh anode operated at
60 kV and 80 mA) at the Instituto de Geología y Minería (Universidad Nacional de Jujuy, Argentina). Majorand minor elements were determined after fusion of thesample using Li borates. Trace elements were measured
on pressed pellets.
Electron microprobe analyses (WDS mode) werecarried out using a JEOL JXA 8900M microprobe
at the Centro de Microscopía Luis Brú (Universidad
Complutense de Madrid, Spain – UC) and a CAMECASX-50 microprobe at the Brigham Young University(Utah, USA – BYU). Standards used for silicates (15 kV,
20 nA, 5 μm beam diameter, Kα lines) at UC were albite(Si, Na), sillimanite (Al), almandine (Fe, Mn), kaersutite (Ti, Mg, Ca), microcline (K), gahnite (Zn) andchalcopyrite (Cu). Counts were acquired for 10 s at thepeak at 5 s at each background position. For sulfides
we used 20 kV, 50 nA, a beam diameter of 2 to 5 μm
and the same count times as for silicates. The lines andstandards were as follows: Lα lines for Ag (pure Ag), As(AsGa), Pb (galena), Sb (GaSb), and Bi (BiTe), and Kαlines for Co, Ni, Cr (FeNiCoCr alloy), Ca (kaersutite),
Fe and Mn (almandine), S and Cu (chalcopyrite), andZn (gahnite). Instrumental parameters used at BYU forsilicates were 10 nA, 15 kV, beam diameter 10 μm, 20 s
count time on peak and 10 s at each side. Only Kα lines
were used. Standards included MgO (Mg), anorthite(Al), chalcopyrite (Cu), orthoclase (Si), wollastonite(Ca), titanite (Ti), spessartine (Mn) and fayalite (Fe).
Data were corrected using the PAP routine (Pouchou andPichoir 1985) (CAMECA) or the ZAF algorithm (JEOL).
Reported detection limits indicated in the respective
tables of mineral analyses or given in the text are at a
2σ level, based on counting statistics. The H 2O content
in dioptase was determined by loss on ignition at 1000 ºC
for 10 hours. All mineral abbreviations are after Whitney
and Evans (2010).
Backscattered electron images and energy-dispersive
spectroscopy (EDS) spectra were acquired using an Amray scanning electron microscope equipped with an EDS
system which detects elements with Z ≥ 11 (Na), housed
at the Earth and Environmental Sciences Department of
the University of New Orleans (USA). Refractive indices were measured using single grains by immersion in
Cargille oils.
Data from the study on fluid inclusions are summarized from Poklepovic et al. (2001). We inform here about
the experimental conditions, which were not reported inthat publication. Microthermometric runs were performed
in a Fluid Inc. heating-freezing stage, calibrated withsynthetic standards. The instrumental precision is ±0.1 C
between –56.6 ºC and 660.4 ºC. Doubly polished sections≤ 300 µm thick were used for microthermometric determinations. Measured data were processed with FLINCOR
software (Brown 1989).
Two calcite and two barite samples were selected toevaluate O, C and S stable isotope data. δ18O and δ13C
values were collected from calcite and δ34S from barite.
The CO2 from vugs-filling calcite was extracted following
the technique of Rosenbaum and Sheppard (1986) after
overnight reaction with 100 % phosphoric acid at 50 ºC.
Sulfur dioxide from barite was extracted by combustion,using a continuous continuous-flow methodology in anelemental analyzer. Barite NBS-127 (from seawater) wasused as a standard.
All isotope ratios were measured on a Finnigan MAT
252 mass spectrometer; isotopic ratios were standardized
to VSMOW (O), PDB (C) and CDT (S). Samples wererun at the Stable Isotope Lab, Department of Geological
Sciences, Indiana University at Bloomington, USA.
301

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

4. Regional geology
The Sierras de Córdoba, part of the Sierras Pampeanas(Pampean Ranges) in central Argentina, are composed ofseveral north–south trending blocks that were lifted andtilted during the Andean orogeny (Tertiary) (Fig. 1a–b).
There are three lithological belts that run along the mountain chains, separated by tectonic contacts: a western domain of low-grade metapelites, an eastern zone of mediumpressure granulite-facies metamorphic rocks derived fromsedimentary and igneous protoliths, and an intermediatezone of middle to high amphibolite facies (Baldo et al.
1996a, b and references therein). Marble is much moreabundant in the eastern than in the remaining two belts.
In the study area, located in the range known as Sierras
Chicas and belonging to the eastern belt as listed above,
two lithological domains have been recognized, separated
by north-trending faults marked by intense mylonitization(Fig. 1c); the metamorphic grade increases eastwards(Gordillo and Lencinas 1979; Baldo et al. 1996a, b; Rapela et al. 1998). The La Calera Group, where the copper
mineralization is located, is composed of Grt–Sil–Crd
meta- to diatexites, along with subordinate gneisses,
amphibolites and diopside marbles. Refractory enclavesof quartz, metaquartzite, amphibolites and orthopyroxene metabasites occur within the migmatites (Baldo etal. 1996a, b). The El Diquecito Group consists of two
assemblages separated by the El Diquecito Fault. Tonalitic orthogneisses interlayered with minor high-grade
paragneisses (Sil + Grt + Kfs) and lenses of marble andamphibolites dominate to the west of the fault. A much
more complex sequence crops out east of the fault,
with Opx–Grt metabasites, tonalitic orthogneisses andmetasedimentary rocks (Sil + Grt gneisses and migmatites). Amphibolites have an N-MORB signature which,when coupled with positive εNd values, strongly indicatesthat they represent relicts of the original oceanic crust(Rapela et al. 1998).
Baldo et al. (1996a, b) and Rapela et al. (1998)
have demonstrated that this area has undergone at least
3 metamorphic events, which they called M1, M2 and M3.
Highest grade (granulite-facies) conditions were reachedduring M2. Two samples of migmatite from La CaleraGroup gave P = 5.7 ± 0.4 kbar and T = 820 ± 25 ºC, and P= 6.3 ± 1 kbar and T = 820 ± 60 °C (Rapela et al. 1998).
High-grade metamorphism related to anatexis has been
dated by SHRIMP on monazite from the same paragenetic association at 522 ± 8 Ma (206Pb/238U) or 534 ± 7 Ma
(208Pb/232Th) (Rapela et al. 1998). Somewhat higher pressure was calculated for a metabasite from El DiquecitoGroup, yielding P = 8.6 ± 0.8 kbar and T = 810 ± 50 °C for
the M2 event (Rapela et al. 1998). Conditions during theretrograde M3 event were estimated at 4 ± 0.5 kbar and715 ± 15 ºC (Baldo et al. 1996a).
302

Unmetamorphosed igneous rocks are scarce. The main
body is the Loma Ancha muscovite granite, a small (lessthan 1 km along the longest axis) pluton. Peraluminous,
barren or poorly mineralized (beryl-bearing) pegmatites
reaching a few tens of meters in length with very simple
mineralogy together with tonalitic dikes are scattered in
all three metamorphic groups.
Cretaceous clastic rocks (conglomerates and sandstones) of continental origin cover discontinuously some
sectors at the eastern flank of the Sierras Chicas.

5. Results

5.1. Geology of the mineralized area
5.1.1. The host rocks
The marble body that hosts the copper mineralization
strikes N 157º E and dips 54º W, and it is composed ofalternating reddish and whitish marble, sometimes withconspicuous bluish staining due to chrysocolla. Nine
marble samples, differentiated by color and mineralogicalvariations, were extracted along a SE–NW profile (Fig. 2
and Tab. 1). Major rock-forming minerals are calcite anddolomite, defining a granoblastic texture with fine tocoarse grain size. Macroscopic color ranges from reddish
to white; in thin section carbonates are cloudy to clear.
Minor phases are graphite, phlogopite and apatite, while
lizardite and possibly tremolite are retrograde.
Graphite is very common as isolated scales and foliated masses up to 1 cm long, and also as inclusions inphlogopite (Fig. 3a–e). X-ray diffraction shows that it is
the 2H polytype, with d002 ranging from 3.349 to 3.339 Å,
indicating a near-maximum degree of order (Luque et al.
1998). The 3R polytype has not been detected.

NW

SE
3
4
1

5

6
7
8

2

9

1m
marble without or with very
low-grade Cu mineralization
marble with abundant Cu mineralization
debris1

sampleFig. 2 Sketch of the quarry face showing the sampling spots as it
appeared in 2005. Since then mining has drastically changed the topography.

Copper mineralization in marble, Córdoba, Argentina

Tab. 1 Marble samples representative of the Esperanza deposit
Sample
M1
M2
M3
M4
M5
M6
M7
M8

Average grain size
3 mm
6 mm
5 mm
5 mm
2 to 8 mm
7 mm
9 mm
4 mm

Color
reddish browngreyish whitepale reddish to greyish
light reddish browngreyishgreyish white with Lz accumulations
light reddish browngreyish with Lz accumulations

Mineralogy
Cal, Dol, Gr, Ap
Cal, Dol, Gr, Ccl, Phl, plancheite
Cal, Dol, Gr, Phl, Ap, Lz
Cal, Dol, Phl, Gr, Ap, Tr
Cal, Dol, Gr, Lz, Phl
Cal, Dol, Phl, Lz, Gr, Ap
Cal, Dol, Phl, Ap, Gr
Cal, Dol, Phl, Gr, Ap, Lz

See Fig. 2 for sample locations.
Abbreviations after Whitney and Evans (2010). Samples in bold are from the zones richest in dioptase.

Phlogopite forms tabular euhedral to subhedral crystals
up to 4 mm long (Fig. 3a, d).
Apatite is very abundant in some samples, as reflected bywhole-rock contents of up to 1.72 wt. % P2O5. It occurs ascolorless rounded grains up to 3 mm across, criss-crossed bynumerous fractures (Fig. 3b). A microprobe analysis showsthat it contains 0.27 wt. % MgO, while Na, Fe, Al, Mn and
Si are below their detection limits (<0.09 wt. % as oxides).
Traces of Cl were detected by EDS analyses.

Lizardite-1T is very common, sometimes giving a palegreen color to the marble in hand specimens. It seems to
be much more abundant in white than in reddish marble.
This phyllosilicate occurs as rounded aggregates up to
2 mm long, macroscopically pale green and colorlessunder plane polarized light in the microscope; they show
the typical finely fibrous texture under crossed polarizers(Fig. 3c). Where lizardite-1T occurs in close proximity toaltered sulfides, it has a green color. In these cases EDS

Tab. 2 Chemical composition of marble found at the Esperanza deposit
wt. %
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
CuO
Na2O
K 2O
P 2O 5
LOI
Total
ppm
Ba
Nb
Zr
Y
Sr
Rb
Ni
Cr
Th
U
Cu
Pb
Zn
Sn

M1

M2

M3

M4

M5

M6

M7

M8

M9

12.72
0.01
0.24
0.45
0.08
9.24
42.86
0.01
0.07
0.01
0.11
32.53
98.33

6.94
0.07
0.16
0.08
0.01
22.15
30.51
1.90
0.00
0.08
0.23
38.18
100.31

8.05
0.06
0.84
0.22
0.02
13.94
38.81
0.80
0.03
0.31
1.72
34.60
99.40

7.53
0.04
0.76
0.08
0.04
5.40
49.27
0.41
0.29
0.31
0.25
35.96
100.34

12.20
0.13
0.28
0.09
0.01
16.04
33.14
1.87
0.00
0.10
0.46
38.48
102.80

9.36
0.06
0.79
0.25
0.01
20.34
31.42
0.71
0.24
0.42
1.10
36.53
101.23

6.55
0.02
0.61
0.17
0.02
15.84
38.66
0.10
0.04
0.15
0.39
35.78
98.33

16.78
0.02
0.39
0.13
0.01
17.93
32.80
1.21
0.02
0.24
1.51
31.94
102.98

9.65
0.06
1.11
0.23
0.01
12.37
39.50
0.25
0.02
0.21
1.20
34.54
99.15

196
2
9
9
58
11
23
3
<1
2
5704
65
9
2

20
1
19
8
73
5
20
<3
<1
<1
776
22
5
<1

40
1
4
5
82
6
21
<3
<1
4
9703
93
10
<1

<20
1
4
8
101
3
18
4
<1
<1
40
4
12
<1

<20
1
2
7
40
4
24
<3
<1
3
15213
29
15
3.8

88
1
13
11
57
7
22
<3
2
2
6356
11
8
<1

71
2
17
9
90
5
17
<3
2
<1
3260
13
5
<1

19
1
6
8
55
3
27
<3
<1
14
14930
89
23
<1

35
2
7
9
60
6
20
<3
<1
<1
1967
7
16
<1

See Fig. 2 for sample locations.
Below detection limits: Ag (<10 ppm), Co (<5 ppm) and Hf (<10 ppm). Note that Cu appears twice, expressed as oxide (wt. %) and in an elemental
form (ppm). Sample M9, not included in Tab. 1, is a reddish marble that extends from the deposit outwards.

303

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

200 mma

500 mm

b
Ap

Gr

Ap

Phl
Phl
Phl

200 mmc

500 mm

d
Ccl
Gr

Lz

e
Ccl

700 mm

Phl

f

Gr

Plan

1 mm
Fig. 3 Photomicrographs [in crossed polars, a to e] and photograph of the marble hosting the mineralization [f ]. a – Phlogopite crystals with graphite
inclusions. b – Two apatite blasts in carbonate. c – Lizardite-1T as a retrograde product after forsterite. d – Fissure filled by banded chrysocolla.
The marble was partially dissolved but graphite flakes are not soluble and remain attached to the walls of the fissure. e – Fissures filled by bandedchrysocolla and spherules of plancheite (Plan). f – Photograph of fissures in marble mineralized with dioptase and calcite. The dashed line marks
the borders of the fissures.

spectra show small amounts of Cu, although it is not clear
whether this element is somehow incorporated within the
lizardite structure or whether it is present as submicroscopic inclusions of some other phase. The shape and texture
304

indicate that it is a retrogression product of forsterite, of
which no relics remain.
Whole-rock analyses of the marbles appear in Tab. 2.
Strongly mineralized samples were not analyzed, but theCopper mineralization in marble, Córdoba, Argentina

pervasive chrysocolla veining cannot be excluded, leading to high Cu values even in samples taken from areas
more than 10 m away from the clearly Cu-rich zone. It
can be seen that no other metal anomaly accompanies
the Cu enrichment. The Mg content indicates that they
are dolomitic marbles, which are common throughout theeastern flank of the Sierras Chicas between 31º 14′ and
31º 22′S. By contrast, calcitic compositions are dominant
when the whole area is considered (Sfragulla et al. 1999).

5.1.2. Structural features
Copper-bearing minerals are concentrated in a lensshaped body, approximately 15 m long, up to 3 m wide
and 10 m deep. The marble lens is cut by faults on boththe northern (where it is in contact with a garnet gneiss)and southern sides. The lens seems to pinch out towards
the E, while the western side has been mined out and norecords as for its shape and dimensions are available.
The mineralization (chrysocolla >> dioptase >>plancheite >> sulfides ≈ tenorite) is found in a networkof fractures mainly hosted in white marble (Fig. 3d–e).
Many fractures were widened by dissolution of carbonates. Non-soluble phases such as graphite are commonly
seen at the contact between the marble and the hydrothermal minerals, but never as inclusions within theselast phases (Fig. 3d). The mean strike of the fissure set
mineralized with dioptase is N30º E dipping 78º W; asubordinate set has an attitude of N13º E/60º E. The main
set is approximately coincident with one of the threemain structural domains (termed D3, with N20º E strike
and a subvertical dip) of the Sierra de Córdoba, which ispossibly of Late Ordovician or Silurian age (Dalla Salda
1984). However, there are many fine fractures, filledwith dioptase or other Cu-bearing silicates, which do notbelong to any of these sets. Some wider fissures (up to
approximately 2 cm wide) are incompletely filled, withpinch-and-swell cavities lined with calcite and dioptase
crystals (Fig. 3f). Calcite-filled fissures without Cu minerals are common throughout the deposit.
Effects of deformation are visible on outcrop scale asductile bending of the marble layers, and also on thinsection scale by bent cleavage planes in carbonates andphlogopite. Mineralization preceded the latest faulting event,as evidenced by slickensides affecting copper silicates.

5.2.	Mineralogy
Hydrothermal minerals include copper silicates (chrysocolla, plancheite and dioptase), tenorite, barite, quartz
and calcite. The inferred paragenetic sequence appears
in Fig. 4. The origin of sulfides is less clear, as discussed
below. Malachite and brochantite occur as alteration
products after sulfides.

early

late

chrysocolla
plancheite.
tenorite
dioptase
calcitebaritequartzanilitespionkopite
covellite
malachitebrochantite
Fig. 4 Inferred paragenetic sequence. The dashed line separates two
different paragenetic associations, the relationship between which is
uncertain.

5.2.1. Chrysocolla
This is by far the most abundant copper mineral, occurring as thin fissure fillings in marble and encrustations
over, or alternating with, calcite, and rarely with dioptase.
Pseudomorphs of chrysocolla after an unknown mineral(most probably a carbonate with rhombohedral crystalsof pseudocubic habit) were found (Fig. 5a).
This silicate is usually pale bluish green, opaque andlacks luster; more rarely it can have a dark blue green
color and greasy luster. X-ray diagrams show that crystallinity (always poor, as is typical of chrysocolla), increases
from the powdery to the porcelaneous variety.
From the chemical point of view, chrysocolla is very
similar to dioptase, although it lacks long-range structuralorder. Chemical analyses of chrysocolla from Córdoba
show very variable H 2O contents (assuming that thedifference between the analytical total and 100 % corresponds to H2O) but a Cu:Si ratio close to the expected 1:1
value. However, compared with dioptase, some elements(especially Mg, Al and Ca, and to a lesser degree Na andK) reach higher concentrations in chrysocolla (Tab. 3).

5.2.2.	Plancheite
This silicate occurs as compact fissure fillings up to 3 mm
thick, sometimes with fibrous structure. It also forms
aggregates of interlocking spherules (up to 2 mm indiameter) with a radiating structure, lining fissure walls;
the remaining space is filled by colorless calcite (Fig. 5b).
Less often plancheite can be found as isolated spherules
completely enclosed in chrysocolla. Color ranges fromlight to medium blue, rarely royal blue; some radial aggregates show concentric banding with a paler periphery.
Massive plancheite is lusterless, but the surface of theradiating aggregates, after being exposed by dissolving
the calcite with dilute HCl, has a silky luster.
305

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

a500 mb

Fig. 5a – Pseudomorph of chrysocolla after an unknown phase (1 cm long), showing a pseudocubic morphology. b – Zoned plancheite spherules
projecting into a calcite-filled fissure.
Tab. 3 Chemical composition of chrysocolla (wt. %)
#12
44.30
0.20
51.87
0.08
2.32
0.25
0.22
0.43

#45
42.12
0.59
57.08
<0.03
0.72
0.37
<0.03
<0.03

#46
36.42
0.08
45.87
<0.03
0.61
0.36
0.04
<0.03

#47
41.26
0.82
55.94
<0.03
0.79
<0.03
0.08
<0.03

#48
35.64
0.21
47.21
<0.03
0.57
0.33
<0.03
<0.03

#38-1
41.03
0.09
49.22
0.06
1.83
0.29
n.m.
n.m.

Total
99.67
apfu on a 18 O basis
Si
6.044
Al
0.032
Cu
5.346
Fe
0.009
Mg
0.471
Ca
0.037
Na
0.057
K
0.075
Σ cations12.071
M:T
0.99

100.88

83.38

98.89

83.96

92.52

SiO2
Al2O3
CuO
FeO
MgO
CaO
Na2O
K 2O

(up to 2.22 wt. % MgO, i.e. up to 0.62
Mg apfu), with lesser Ca (up to 0.32 wt.
% CaO), Al (up to 0.11 wt. % Al2O3), Fe(up to 0.06 wt. % FeO) and Mn (up to 0.08
wt. % MnO). Sodium (up to 0.23 wt. %Na2O) and K (up to 0.43 wt. % K2O) arealso present. Titanium is below the detection limit (0.09 wt.% as TiO2).

5.2.3. Dioptase

This copper silicate forms prismatic crystals that can reach over 20 mm long and
6 mm thick, with a typical length : width
ratio of ~4. They occur included in calcite
or growing in open fissures, isolated or
forming divergent groups (Fig. 6a–d).
Most crystals are morphologically simple,
dominated by the {101̄0} prism terminatedby {112̄1} rhombohedron, sometimes
11.962
combined with other forms of minor de0.98
velopment (Angelelli et al. 1983). Thin
M = Fe + Mg + Ca + Cu + Na + K; T = Si + Al. Measured on a JEOL instrument except
compact veins of granular dioptase arefor #38-1.
more common towards both sides of then.m.: not measured.
mineralized outcrop. Dioptase is translucent to transparent, with a bright to dark green color and
The X-ray powder diffraction patterns show very
vitreous luster. Some crystals display an incipient alterabroad peaks, with a full width at half maximum valuetion, turning opaque and with dull luster (Fig. 6e). Asof 1.15º (2θ) for the 020 reflection at 8.43º (2θ). Unitmentioned above, crystals are fragile due to the perfectcell dimensions (refined in the space group Pcnb) arecleavage on {101̄1}. X-ray diffraction data show excela 19.04(4), b 21.02(4), c 5.19(1) Å, V 2076(6) Å3. The
lent agreement with those reported in the card 01-072diffraction patterns match that of card 01-083-1241 of1956 of the PDF-JCPDS; refined unit-cell parameters (inthe Powder Diffraction Files of the Joint Committee on
the space group R3̄) are a 14.5719(6), c 7.7799(3) Å, V
Powder Diffractions Standards (PDF-JCPDS).
1430.7(1) Å3. In plane polarized light dioptase is intense
The ideal chemical formula of plancheite is Cu8(Si8O22)
green with no pleochroism; measured refractive indices(OH)4·H2O. Chemical analyses (Tab. 4) show that theare ω = 1.656(3), ε = 1.707(3) with a small anomalous
Córdoba samples can contain important amounts of Mg
306

5.838
0.096
5.974
0.002
0.149
0.055
0.000
0.000
12.114
1.04

6.018
0.016
5.724
0.000
0.150
0.064
0.013
0.000
11.985
0.99

5.829
0.137
5.969
0.000
0.166
0.000
0.021
0.000
12.122
1.03

5.911
0.040
5.914
0.000
0.141
0.059
0.000
0.000
12.065
1.03

6.030
0.015
5.464
0.007
0.401
0.045

Copper mineralization in marble, Córdoba, Argentina

Tab. 4 Chemical composition of plancheite (wt. %)
#38-4
42.72
0.04
<0.03
0.02
1.88
0.16
51.73
n.m.
n.m.
4.78

#38-5
42.93
0.05
0.04
0.00
2.04
0.19
50.18
n.m.
n.m.
4.76

#38-6
43.31
0.04
0.09
0.00
1.89
0.22
51.20
n.m.
n.m.
4.81

#A-a
43.41
0.09
0.06
<0.06
1.89
0.29
49.00
0.23
0.43
4.76

#A-b
43.46
0.09
<0.05
<0.06
1.99
0.28
49.17
0.16
0.32
4.77

#B
44.08
0.11
<0.05
0.08
2.22
0.32
48.37
0.14
0.41
4.82

Total
101.86101.33
apfu on a 24 O equivalent basis
Si
8.076
8.037
Al
0.009
0.008
Fe
0.009
0.000
Mn
0.000
0.003
Mg
0.518
0.527
Ca
0.045
0.032
Cu
7.258
7.351
Na
–
–
K
–
–
H calc6.000
6.000
Σ cations*15.91515.958100.19101.56100.16100.24100.55

8.105
0.011
0.006
0.000
0.573
0.038
7.155
–
–
6.000
15.888

8.090
0.009
0.013
0.000
0.525
0.044
7.223
–
–
6.000
15.904

8.193
0.019
0.009
0.000
0.533
0.058
6.985
0.085
0.102
6.000
15.984

8.182
0.019
0.002
0.000
0.560
0.056
6.991
0.058
0.077
6.000
15.945

8.226
0.024
0.000
0.013
0.616
0.065
6.817
0.050
0.098
6.000
15.909

SiO2
Al2O3
FeO
MnO
MgO
CaO
CuO
Na2O
K 2O
H2O calc

#38-2
43.31
0.04
0.06
0.00
1.87
0.23
51.53
n.m.
n.m.
4.82

Measured on a CAMECA instrument except for #A-a, #A-b and #B. H 2O content calculated by stoichiometry. Zinc was found to be below about 1000 ppm (2σ) in all cases.
n.m.: not measured.
*Calculated H apfu not included in the sum of cations.

a

d

2 mm

1 mm

b

e

1 mm

4 mm

2V. Refractive indices fall within the range given by Anthony
et al. (2001): 1.652–1.658 for ω
and 1.704–1.710 for ε.
Even though dioptase fromother localities may show minor but significant substitutions at the Cu site, mainly
Ca, Mg and Zn (e.g., Pauliš etal. 2006), electron microprobe
analyses (Tab. 5) show that the
dioptase from Córdoba has analmost stoichiometric composition, with only small amountsof Mg (0.06–0.15 wt. % MgO,
0.01–0.03 apfu Mg). Iron and
Al are present in quantities
close to, or below, the detection limit (≤ 0.03 wt. % of
their oxides), whereas Mn, Ca,
Ti and Zn are always below
their respective detection limits(300–1000 ppm, depending on
the element). No systematicchanges were observed between
cores and rims of the crystals.
The slight deviations from thestoichiometric values (ideally
38.93 wt. % SiO2, 49.51 wt. %CuO) are considered to be an
artifact, probably because chal-

c

2 mm

f

2 mm

Fig. 6 Dioptase crystals. a to d – Dioptase crystals growing on calcite. e – Dioptase with altered surface, evidenced by concentric rings. f – Crustof calcite microcrystals overgrowing dioptase.

307

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

Tab. 5 Chemical composition of dioptase (wt. %)5.2.4. Calcite#39-1-b
38.87
0.03
<0.03
51.01
0.24
11.91

#39-1-ia
38.76
0.03
0.04
51.04
0.30
11.91

#39-1-ib
38.67
<0.03
0.05
52.05
0.17
11.91

#39-1-c
38.78
0.03
0.03
52.49
0.13
11.91

#50
39.61
<0.03
0.03
49.99
0.15
11.91

#51
40.65
0.06
<0.03
51.50
0.06
11.91

Total
102.06
apfu on a 18 O basis
Si
5.996
Al
0.006
Fe
0.000
Cu
5.943
Mg
0.055
H
6.130
Σ cations18.130102.08102.85103.37101.69104.18

5.982
0.005
0.005
5.950
0.070
6.133
18.145

5.951
0.000
0.006
6.050
0.038
6.116
18.161

5.941
0.006
0.003
6.074
0.029
6.088
18.141

6.081
0.000
0.004
5.797
0.034
6.100
18.016

6.077
0.011
0.000
5.815
0.013
5.941
17.857

SiO2
Al2O3
FeO
CuO
MgO
H2O meas

Measured on a CAMECA instrument except for #50 and #51.

copyrite (instead of an oxygen-containing material) wasused as a Cu standard or to the data reduction software.
An analysis of dioptase from this quarry made using
gravimetric methods was published by Angelelli et al.
(1983), who reported 38.00 wt. % SiO 2, 50.40 wt. %CuO and 11.52 wt. % H2O, total 99.92 wt. %. This corresponds to Cu6.00(Si6.07O18)·6.07H2O.

Among the hydrothermal minerals,
calcite is the most abundant phase,
forming scalenohedral or rhombohedral
colorless, whitish or very pale yellow
crystals up to 4 cm long and sometimes twinned on {0001}. Most often
crystals show an incipient dissolution,
giving them a somewhat greasy luster.
Coarse-grained masses filling fissures
are common throughout the deposit.
A late generation of very fine grained,
lusterless grayish calcite covers somesurfaces in cavities, sometimes displaying a fine banding. It is most likely that
this generation precipitated from percolating meteoric water and it is probably
unrelated to the mineralization process.

5.2.5.	Barite
Very rare barite occurs as groups of crystals of up to
9 mm long, tabular on {001} with smaller {100}, {011},{110} and {111}. Color ranges from pale to bright yellow, often with concentric color zoning visible along[001]. Crystals are always implanted on calcite and rarely

Tab. 6 Electron microprobe analyses of sulfides (wt. %)

Bi
S
Cd
Pb
Cu
Sb
Fe
Ag
Total
apfu
S
Bi
Cd
Pb
Cu
Sb
Fe
Ag
Σ cations(Cu+Fe)/S

#2
0.11
22.26
<0.03
0.08
76.71
0.05
<0.02
0.02
99.23

#8
0.09
22.54
<0.03
0.09
77.13
0.10
<0.02
0.04
99.98

#9
0.06
22.35
<0.03
0.10
76.82
0.07
<0.02
<0.02
99.40

anilite
#10
0.13
22.49
<0.03
0.12
76.74
0.06
<0.02
0.03
99.57

#4
0.07
22.49
<0.03
0.09
75.60
0.04
0.03
0.02
98.34

#5
<0.05
21.84
<0.03
0.12
76.41
0.05
<0.02
<0.02
98.42

#6
0.07
22.40
<0.03
0.11
76.53
0.04
<0.02
<0.02
99.14

covellite
#3
#7
0.08
0.15
33.51
33.72
<0.03
0.03
0.16
0.15
65.38
64.61
0.05
0.03
0.05
<0.02
0.06
<0.02
99.28
98.69

spionkopite
#1
#11
0.13
0.08
24.17
25.16
<0.03
<0.03
0.06
0.13
68.73
67.52
0.06
0.06
6.36
7.15
0.03
0.02
99.55
100.12

4.00
0.00
0.00
0.00
6.95
0.00
0.00
0.00
6.96
1.74

4.00
0.00
0.00
0.00
6.91
0.00
0.00
0.00
6.92
1.73

4.00
0.00
0.00
0.00
6.94
0.00
0.00
0.00
6.95
1.74

4.00
0.00
0.00
0.00
6.89
0.00
0.00
0.00
6.90
1.73

4.00
0.00
0.00
0.00
6.78
0.00
0.00
0.00
6.80
1.70

4.00
0.00
0.00
0.00
7.06
0.00
0.00
0.00
7.07
1.77

4.00
0.00
0.00
0.00
6.90
0.00
0.00
0.00
6.90
1.73

1.00
0.00
0.00
0.00
0.98
0.00
0.00
0.00
0.99
0.99

5.00
0.00
0.00
0.00
7.17
0.00
0.76
0.00
7.94
1.59

1.00
0.00
0.00
0.00
0.97
0.00
0.00
0.00
0.97
0.97

5.00
0.00
0.00
0.00
6.77
0.00
0.82
0.00
7.60
1.52

Formulae normalized on a basis of 4 (anilite), 1 (covellite) or 5 (spionkopite) sulfur atoms per formula unit.
Also sought for but not detected, with detection limits (2σ, in ppm): As (340), Co (260), Ni (260), Zn (520), Ca (120) and Mn (260). Analyses
carried out by JEOL microprobe.

308

Copper mineralization in marble, Córdoba, Argentina

in contact with dioptase. Elements detected using EDS
are major S and Ba, and trace amounts of Sr.

5.2.6. Tenorite
Dull, blackish brown masses and stringers included inmarble were identified by X-ray diffraction as tenorite,with broad peaks indicative of very small crystallite
size. Textural relations with copper silicates suggest that
tenorite crystallized later, at least relative to plancheite
and the first chrysocolla stage.

5.2.7. Copper sulfides; malachite andbrochantite
Very scarce grains of copper sulfides are found as inclusions in the marble. Macroscopically they are grayish
black with a thin dark blue rim. Electron microprobe
analyses (Tab. 6) show that the core is composed ofanilite, which is partly replaced by covellite and small
amounts of spionkopite along the rims and cracks(Fig. 7). In addition to the essential structural constituents, sulfides contain traces of Bi (≤0.15 wt. %) and Pb(≤0.16 wt. %). Silver and Sb are present just above thedetection limits (c. 250 ppm, at 2σ).
Fibrous masses of malachite and brochantite (bothconfirmed by powder XRD and EDS) occur partiallysurrounding the sulfide grains (Figs 7a–b).
Sulfides (and secondary malachite and brochantite)cannot be unequivocally inserted in the paragenetic
sequence mentioned above, as they occur in a different
brochantiteamicro-environment (granular marble, as opposed to fissure fillings) and do not display cross-cutting relationships with other copper minerals. The chrysocolla films
surrounding and crossing some sulfides are an exception,
but they could have a local origin and be unrelated tochrysocolla associated with dioptase and plancheite. At
present it is not known whether sulfides were deposited
during the same mineralizing event or they pre-dated thesilica-rich minerals.

5.3. Fluid inclusions
The results of a fluid inclusions study were briefly summarized by Poklepovic et al. (2001), and are presented
in full here. The study was aimed at obtaining insight
into the temperature and fluid composition that prevailed
during the precipitation of copper minerals. Therefore,
only primary inclusions were measured; a careful search
revealed useful fluid inclusions only in dioptase.
Fluid inclusions occurring in sections representing
five different crystals of dioptase are irregularly shaped
and occur as clusters or isolated. The size of individual
inclusions ranges from 11 to 25 μm. Fluid inclusions
show two phases (L + V), with a degree of fill (F) of~0.7. Fluid inclusions lack daughter crystals, but a few
accidentally trapped opaque solids were seen in several
cases. Homogenization temperatures (Th) vary between
217 and 311 ºC, with a mean of 259 ºC (n = 33), whereas
ice-melting temperatures (Tmi) range from –0.9 to 0.0 ºC(n = 27). No CO2 was detected during the freezing runs.
Calculated salinities are thus very low, from 0 to 2 wt. %bcalcitelizarditemalachitecovelliteanilitechrysocolla

50 mapatiteanilite50 mFig. 7 Backscattered electron images of sulfides and their alteration products. a – Anilite relics with covellite along fissures, separated by a networkof brochantite. b – Grain of anilite in marble, partially altered to malachite and chrysocolla.

309

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

NaCl equivalent (Fig. 8). The restricted compositionalvariation and approximately constant value of F imply
that the hydrostatic pressure was larger than the vapor
pressure, preventing boiling. Accordingly, no macroscopic evidence suggestive of boiling or extensional
structures, such as breccias, calcite with bladed habit orinfill textures, was observed. This means that the measured homogenization temperatures are in fact minimum
values, but unfortunately no clues regarding confiningpressure during dioptase precipitation were unraveled.
Gas-rich, irregular secondary inclusions are arranged
along {112̄1} cleavage planes or fractures, becoming
more abundant were these discontinuities intersect.
Necking-down is widespread in secondary inclusions,with daughter crystals present in the fluid-rich portions.
The wide and continuous variation of homogenization
temperature combined with the narrow range in salinity(Fig. 8) is interpreted as reflecting a simple cooling path.
The examined calcite samples (at least 7 cleavage
fragments taken from each of the two specimens used
for isotopic analyses) have curved planes decorated bytiny (mostly ≤4 µm) fluid inclusions, clearly showing thatthey are sealed fractures. Although Th were not measured,
the high F values (estimated at above 0.95) suggest a low
trapping temperature, possibly below 150 ºC. A few larger
inclusions were seen in these planes; however, in addition to being of secondary origin, they show prominent
necking-down features such as long, thin tapering tails
and variable F values. No inclusions with textural features suggestive of a primary origin were found in eitherof these samples, or in a few other calcite specimens.
The only examined barite crystal lacks fluid inclusions.

330
310

Frequency290

Th [ºC]

270
250
230
210
190
170

5.4.	Analysis of stable isotopes

The two analyzed colorless, coarse-grained calcite
samples occur in contact with dioptase and were takenfrom the central part of completely filled fissures. Some
dioptase crystals occurring with calcite texturally similar
to this display irregular surfaces where they are in contact
with the carbonate, indicating precipitation simultaneouswith calcite crystals. Therefore, we assume that the isotopic characteristics of the carbonate reflect those of themain mineralization event.
The two calcite samples are isotopically rather similar
to each other (Tab. 7), and compare fairly well to δ13C
values of high-grade regional marbles that crop out in thevicinity. In the Michelotti quarries at La Calera town, thedolomitic–calcitic marble yielded a δ13C value of 0.5 ‰(± 0.1 ‰), and in the Ferreyra quarries at Malagueño, theδ13C value of a calcitic marble was 0.9 ‰ (Panarello et al.
1980). The studied Esperanza quarry can be consideredpart of the Michelotti quarries from a regional geologic
perspective, whereas the Malagueño quarries, located
15 km to the south, belong to the same metamorphic
belt. Panarello et al. (1980) found a range from 4.6 to–1.4 ‰ δ13C for a suite of Cambrian dolomitic and calcitic marbles representative of the easternmost range of
the Sierras Pampeanas Orientales in Córdoba Province(including the Michelotti and Ferreyra quarries). The
δ18O compositions of these marbles were not measured by
Panarello et al. (1980). Nevertheless, the δ18O values of
Cal–1 (17.1 ‰) and Cal–2 (15.1 ‰) plot well within the
known ranges for metacarbonates from other regions of
the Sierras Pampeanas Orientales. The Tab. 7 lists the different calculated values of δ18O
for water in isotopic equilibriumwith calcite at 300 ºC and 250 ºC.
Regardless of the chosen equation and temperature, all calcu20
lated H2O isotopic compositions
plot within the Metamorphic Water Box (Kerrich 1987). It should15
be remembered that isotopic
values were calculated using the10
homogenization temperaturesof fluid inclusions, which havenot been pressure-corrected be5
cause of insufficient pressure
constraints. Therefore, the trapping temperature is higher; this0
is why the results calculated
100 150 200 250 300 350 400
Th [°C]
using 300 ºC are probably closer

150
0

2

4
Salinity [wt.% eq NaCl]

310

6

8

Fig. 8 Plot of salinity vs. temperature ofhomogenization (Th) for fluid inclusions
in dioptase. Inset: histogram showing the
distribution of Th.

Copper mineralization in marble, Córdoba, Argentina

isotope data arenecessary to further constrain thefluid source. The
isotopic signaturec l o s e l y c o n c o rdant with the local
9.66
15.07
marble can be ex7.64
13.10
plained by a very
low water/rock ratio, which caused an oxygen isotope shift. The enclosing
marble was most likely the source of Ca2+ and (CO3)2– forcalcite deposition, through dissolution–reprecipitation.
Comparable isotopic compositions were calculated by
Lira et al. (2008) for water in equilibrium with epidote
and clinozoisite from retrograde skarns elsewhere in the
Sierras Pampeanas Orientales of Córdoba Province. The
heavy δ18OH2O and δ2HH2O computed from both epidotegroup minerals were interpreted as reflecting the inheritedisotope composition of the skarn garnet they replaced,
which grew at the expense of metasedimentary protolithic
phases.
Sulfur isotopic fractionation in hydrothermal ore
deposits is a complex function of temperature, pH,
fO2, original isotopic composition and sulfur speciation(mainly SO42– and H2S) in the fluid (Ohmoto and Rye
1979). Fortunately, it has been shown that sulfur isotopic
patterns are preserved during metamorphism (e.g., Cookand Hoefs 1997 and references therein; Alirezaei and
Cameron 2001; Russell et al. 2010) and that the directoxidation of sulfide to sulfate provides only minimum
fractionation (e.g. Canfield 2001).
An origin of sulfur exclusively from seawater canbe discarded, as shown by curve depicting the secularvariations of δ34S in seawater sulfate (Seal 2006). Thisprecludes some common sulfur sources such as evaporite
minerals, phosphate-bound sulfate, carbonate-associatedsulfate and marine barite, as all these would be expected
to show the seawater signature (Turchyn et al. 2009).
Considering the geological context, some of the possible sources of sulfur closest to the studied copper mineralization are sulfides dispersed in the marble itself, incalc-silicates interleaved in the metamorphic sequence,
and as accessory phases in ortho-amphibolites.
Sedimentary sulfides display a wide range of δ 34S
values, from less than –50 to over +20 ‰, althoughmost have negative values due to Rayleigh fractionationof sulfur isotopes during the diagenetic bacterial sulfate
reduction (Seal 2006). Unfortunately there are no dataon the sulfur isotopic composition of marble-hosted sulfides from the deposit or, indeed, the rest of the Sierras
Pampeanas Orientales.
Calc-silicate rocks are the result of regional metamorphism of mixed clastic and carbonate protoliths, without

Tab. 7 Isotopic analyses of calcite and calculated values for δ18OH2O for water in equilibrium with calcite
SampleCal-1
Cal-2

δ C (‰)

δ O (‰)

0.9
0.4

17.1
15.1

13

Cal-1
Cal-2

18

Calculated values of δ18OH2O for water in equilibrium with calcite at 300 ºC (‰)
O’Neil et al. (1969) and
Zheng (1999)
Kim and O’Neil
Friedman and O’Neil (1977)(1997)
11.5
11.3
18.1
9.5
9.3
16.1
Calculated values of δ18OH2O for water in equilibrium with calcite at 250 ºC (‰)
9.84
7.82

to the actual isotopic values of the fluid, even though theaverage Th (not pressure-corrected) is 259 ºC.
Two δ34S values recorded by barite from the Esperanza
quarry fall within the range 3.6 to 4.6 ‰ CDT. Just a
few samples of barite were found, and the very restricted
position of this sulfate in the paragenetic sequence (seeFig. 4) suggests that the tight range of δ34S values may
indeed be representative of the Esperanza showing. Unfortunately, the copper sulfides also present are too scarce
to be analyzed with the available techniques.

6. Discussion
As described above, the fluid that deposited copper silicates, calcite and barite was hot (with maximum temperature above 300 ºC, considering that a pressure correction
to the measured Th should be applied) and very dilute(0–2 wt. % eq. NaCl).
Such homogeneous, very low salinity is typical of
fluids of meteoric origin (e.g., Richards and Spooner
1989; Seal and Rye 1993; Craw 1997; Bajnoczi et al.
2000; Moritz 2006; Fernández et al. 2008), although it
is not unknown from other systems such as porphyry
Cu (± Mo) deposits (e.g. Gammons and Williams-Jones
1997; Rusk and Reed 2008; Sillitoe 2010). However, inmost of these latter cases, low-salinity fluids are foundsolely in one of several fluid inclusion assemblages, theothers having higher salinities (e.g. Pudack et al. 2009).
In addition to that, in many cases the meteoric water isindeed involved in these hydrothermal systems, this being
one of the causes for the low-salinity fluids (e.g. Zhang
et al. 1989). Fluids of metamorphic origin can also have
low salinity, but they usually contain carbon compounds
such as CO2 or CH4 (e.g., Naden and Shepherd 1989;
Witt et al. 1997; Mishra and Pal 2008). These gases arealso rather common in fluids of igneous origin. Given
the absence of nearby intrusive centers (see below), andconsidering that the copper mineralization postdated theregional metamorphic peak, we prefer the hypothesisthat the fluids responsible for the copper mineralization
had a dominantly meteoric origin, consistent with their
low salinity and absence of gases (detectable by freezing
measurements) other than H2O vapor. Additional stable311

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

appreciable elemental input from an external source.
Therefore, any sulfide occurring in these rocks shouldshare the isotopic characteristics discussed above for the
marble protoliths.
Any evidence of magmatic activity that could havebeen a direct source of hydrothermal fluids and elements
is lacking in the area. However, nearby ortho-amphibolite
bodies could host sulfides with magmatic-like δ 34S(mostly 0 ± 5 ‰), which on dissolution would provide
a suitable S source for barite. A high SO42–/H2S ratio isinferred from the absence of sulfides in the paragenetic
association at the Esperanza showing. Under these conditions, barite precipitated at 200 ºC from a fluid with δ34S∑S= 0 ‰ would have a δ34S value of +3.2 (Rye and Ohmoto1974), comparable to those found in this work.
Other possibility that should be considered is the factthat the δ34S value of c. +4.1 may have resulted from themixing of solutions carrying contrasting δ34S signatures,such as a light source derived from oxidation of sedimentary sulfides and a heavy one from seawater-related
sulfate. On the other hand, the two closely comparable
values of δ34S in barite available for the deposit do notprovide further support for such a mixing hypothesis.
A related issue is the source of copper. The same candidates mentioned above as possible sources of sulfur(namely sulfides scattered in the marble, in calc-silicate
rocks or in amphibolite) could have conceivably released
copper as well.
Copper mineralization hosted in dolomitic marbles
is known from different deposits (none of economicalsignificance) and showings scattered in the Sierras Pampeanas of Córdoba, the most relevant localities being the
Cañada de Álvarez and Atos Pampa districts (Fig. 1b).
Primary mineralization consists mainly of chalcocite,with traces of chalcopyrite, pyrrhotite, bornite, digenite,
gold, and possibly wittichenite and silver. Malachite,
dioptase and pseudomalachite are found among the
Cu-bearing secondary species (Brodtkorb et al. 1981).
As yet, there is no consensus regarding the source ofthe copper. Some researchers have postulated an origin
related to bio-mineralization by algae, under reducing
conditions in a restricted marine basin (Brodtkorb et al.
1981; Mutti et al. 1998). However, the Cu-rich layers
are locally discordant to the marble foliation, implyingthat if the biogenic origin could be proven then there has
been at least some local hydrothermal remobilization.
As an alternative, Mutti and Di Marco (1999) suggested
that the intercalations of tholeiitic metabasalts with
MORB signature within the carbonate sequence support a hypothesis that copper could have been related
to submarine exhalations, and that the deposit could bebetter classified as a SEDEX-type. However, more data
are needed to provide additional support to either of thetwo competing hypotheses.
312

Another possible source are amphibolites, which are
known to be genetically related to very small deposits
found along the Sierras of Córdoba. The metallic association is Cu + Fe (± Zn, Au, Ag, Co), represented by chalcopyrite and magnetite with varying amounts of pyrite,
pyrrhotite, hematite, bornite, sphalerite, silver, carrolite,
and ilmenite. Tetrahedrite and gold are rare accessories(Mutti and Di Marco 1999 and references therein). The
copper content of non-mineralized amphibolites is up to
240 ppm, although most values are very low, close tozero (Daziano 2004).
No metallic anomaly such as any of those mentioned
above is found within a reasonable distance (tens ofkm) of the Esperanza showing. Therefore, and unless aburied or eroded source is invoked, the copper shouldhave been released from copper (± other metals) sulfide
grains present as accessory phases in the barren marble
or amphibolite.
The absence of copper carbonates could be explainedby the abundance of Ca2+ in the mineralizing solutions.
Under these conditions, the solubility product of calcite
would be reached before that of copper carbonates. Also,a low ratio of PCO /aSiO2 should stabilize chrysocolla
instead of malachite (see Crane et al. 2001). Malachite isfound to be restricted to the immediate surroundings ofaltered sulfides, where aCu was high enough to stabilize
this mineral. The sequence plancheite → dioptase →quartz involves an increase in aSiO2/aCu. Experiments
have shown that the conditions leading to chrysocolla
precipitation are low Cu activity, SiO2 concentration below that yielded by equilibration with amorphous SiO2,
and medium to high pH (5–9) (Newberg 1967; Yates et al.
1998). For solutions at the pH range expected in systems
buffered by calcite and CO2 (between 9.95 and 8.31, but
usually closer to the lower value; Sato 1960) that are very
dilute and with low Cl contents, the dominant Cu species
is Cu(OH)20, followed successively by Cu(OH)+, Cu2+ andCu2(OH)22+ (Yates et al. 1998).
The identity of primary sulfides in the marble remains
unknown, as anilite is usually the product of copper
leaching of a precursor mineral (e.g., Hatert 2005), but
no relics of such a putative primary sulfide were detected.
Further leaching leads to the sequence spionkopite →covellite (Goble 1981).
The heat source is enigmatic. Four episodes of crustal
heating on a regional scale took place after the Cambrianmetamorphic event, all accompanied by igneous activity.
The first magmatic event occurred during the Pampean
Orogeny (Cambrian), producing metaluminous, calcalkaline granitoid sequences; also related to a later phaseof this orogeny are strongly peraluminous granitoids
and pegmatites (Rapela et al. 1998). Sodium-rich trondhjemitic and granodioritic plutons were intruded during
the Famatinian Orogeny (Ordovician), followed by a2

Copper mineralization in marble, Córdoba, Argentina

pegmatite swarm (Rapela et al. 1998). The largest igneous body in the region is the Devonian Achala Batholith,
dated on zircon (U–Pb) between 379 ± 4 and 368 ± 2 Ma
(Dorais et al. 1997; Rapela et al. 2008). However, thenearest outcrops of the batholith are found 13 km W of
the dioptase occurrence. Finally, alkaline basalts were
erupted or formed dikes during an aborted Cretaceous
rifting event (Kay and Ramos 1996). Fluorine remobilization leading to intragranitic fluorite mineralization,
dated at 131 ± 22 Ma (La Nueva lode, inside the Achala
Batholith), was possibly related to heat transfer due tothis basic magmatism (Galindo et al. 1997). However, it
should be stressed that there are no igneous rocks in theproximity of the dioptase occurrence.
A metamorphic origin of the fluids should be considered, given the isotopic signature of calcite and lack ofrelated igneous bodies that otherwise could be an evident
source of heat and elements. Most of the fluid-releasing
reactions are likely to occur during the prograde stage(Pirajno 1992). However, the open cavities frequent in
the Esperanza quarry indicate that the mineralization
postdated the last metamorphic event, but any evidence
for metamorphism that could have mobilized hydrothermal solutions after the marble was partially uplifted andfractured is lacking.
One alternative could be the circulation of water
caused by the Tertiary uplift of Paleozoic blocks forming
the Sierras Pampeanas as a result of the more westerly
shortening due to the Andean Orogeny (Baldo et al.
1996a). However, this scenario remains purely speculative.

7. Conclusions
The studied marble-hosted copper mineralization at
Saldán, Córdoba Province (central Argentina), consisting mainly of chrysocolla, dioptase and plancheite withvery subordinate barite, is not part of the supergenezone of a metallic deposit. The copper source could not
be tightly constrained by the information presented inthis contribution, but the geological evidence (including
isotope data) points towards copper mobilization fromcountry rocks by very dilute hydrothermal (T ~ 300 ºC)
solutions of meteoric origin. The most likely candidates
are marbles (which contain small amount of Cu sulfides)
or amphibolites.
Acknowledgements. SECyT-UNC provided partial financial support for this project. Beatriz Coira and Patrocinio Flores (Instituto de Geología y Minería, Jujuy) aregratefully acknowledged for the whole-rock chemical
analyses. Michael Dorais (Brigham Young University,
Provo) allowed RL to perform some of the electron mi-

croprobe analyses reported here. Radek Škoda (Masaryk
University, Brno) kindly sent a copy of a publication on
Czech dioptase. William Simmons and Alexander Falster(University of New Orleans) are thanked for access to theSEM. Jorge Sfragulla (Universidad Nacional de Córdoba)
kindly brought to our attention the isotopic values ofmarbles from Córdoba. We are very grateful to Zdeněk
Dolníček (Palacký University, Olomouc) and Martin
Okrusch (Julius-Maxmilians-Universität Würzburg) for
constructive and detailed reviews and to the Editors Stuart Mills, Jakub Plášil and Vojtĕch Janoušek for careful
editorial handling.

References
Alirezaei S, Cameron EM (2001) Variations of sulfur isotopes in metamorphic rocks from Bamble Sector, southern Norway: a laser probe study. Chem Geol 181: 23–45
Angelelli V, de Brodtkorb MK, Gordillo CE, Gay HD(1983) The Mineral Species of the Argentine Republic.
Special Publication of Servicio Minero Nacional, Subsecretaría de Minería, Buenos Aires, pp 1–528 (in Spanish)Anthony JW, Bideaux RA, Bladh KW, Nichols MC (eds)(2001) Handbook of Mineralogy. Volume I. Mineral Data
Publishing, Tucson, pp 1–446
Bajnoczi B, Molnar F, Maeda K, Izawa E (2000) Shallow
level, low-sulphidation type epithermal systems in theRegec Caldera, Central Tokaj Mts., NE-Hungary. Geol
Carpath 51: 217–227
Baldo EG, Casquet C, Galindo C (1996a) The metamorphism of the Sierra Chica of Córdoba (Pampean Ranges),
Argentina. Geogaceta 19: 51–54 (in Spanish)
Baldo EG, Demange M, Martino RD (1996b) Evolutionof the Sierras de Córdoba, Argentina. Tectonophysics
267: 121–142
Bérar J-F, Lelann P (1991) E.S.D.’s and estimated probable error obtained in Rietveld refinements with local
correlations. J Appl Crystallogr 24: 1–5
Brodtkorb MK de, Hillar N, Ametrano S (1981) Copper
showings present in the limestone quarries of Cañadade Álvarez, Córdoba Province. In: Proceedings of the 8º
Congreso Geológico Argentino, San Luis 2: pp 851–861(in Spanish)
Brown PP (1989) FLINCOR: a microcomputer program forthe reduction and investigation of fluid-inclusion data.
Amer Miner 74: 1390–1393
Canfield DE (2001) Biogeochemistry of Sulfur Isotopes. In:
Valley JW, Cole DR (eds) Stable Isotope Geochemistry.
Mineralogical Society of America and Geochemical
Society Reviews in Mineralogy and Geochemistry 43:
607–636
Cook RB (2002) Dioptase: Tsumeb, Namibia. Connoisseur’s
Choice. Rocks & Minerals 77: 176–180
313

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del Tánago

Cook RB (2003) Letters to the Editor – dioptase update.
Rocks & Minerals 78: 151–152
Cook NJ, Hoefs J (1997) Sulphur isotope characteristics ofmetamorphosed Cu–(Zn) volcanogenic massive sulfide
deposits in the Norwegian Caledonides. Chem Geol
135: 307–324
Cook RB, Nicolson BE (2002) The occurrence of dioptase
in African mineral deposits. Mineral Rec 33: 77–78
Crane MJ, Sharpe JL, Williams PA (2001) Formation ofchrysocolla and secondary copper phosphates in thehighly weathered supergene zones of some Australiandeposits. Rec Australian Mus 53: 49–56
Craw D (1997) Fluid inclusion evidence for geothermal
structure beneath the Southern Alps, New Zealand. New
Zeal J Geol Geop 40: 43–52
Dalla Salda LH (1984) The intimate structure of the Sierra
de Córdoba. Rev Asoc Geol Arg 39: 38–51 (in Spanish)
Daziano CO (2004) The amphibolites of the Sierra Chicaof Córdoba, Argentina. Publicaciones de la Universidad
Nacional de Córdoba, Córdoba, pp 1–130 (in Spanish)
Dorais MJ, Lira R, Chen Y, Tingey D (1997) Origin of biotite–apatite rich enclaves, Achala Batholith, Argentina.
Contrib Mineral Petrol 130: 31–46
Fernández RR, Blesa A, Moreira P, Echeveste H, Mykietiuk K, Andrada de Palomera P, Tessone M (2008)
Gold and silver deposits related to Jurassic Patagonian
volcanism: review and perspectives for exploration. Rev
Asoc Geol Arg 63: 665–681 (in Spanish)Friedman I, O’Neil JR (1977) Compilation of stable isotope fractionation factors of geochemical interest. In:
Fleischer M (ed) Data of Geochemistry. United States
Geological Survey Professional Paper 440–KK, 6th edition, Reston, pp 1–49
Galindo C., Pankhurst RJ, Casquet C, Coniglio J, Baldo
EG, Rapela CW, Saavedra J (1997) Age, Sr- and Ndisotope systematics, and origin of two fluorite lodes,
Sierras Pampeanas, Argentina. Int Geol Rev 39: 948–954
Gammons CH, Williams-Jones AE (1997) Chemical mobility of gold in the porphyry–epithermal environment.
Econ Geol 92: 45–59
Gay HD, Gordillo CE, Labudía CA (1975) Plancheite
Cu8(Si4O11)2(OH)4·H2O of the Nucha mine, Unquillo(Córdoba). Rev Asoc Arg Miner Petrol Sedim 6: 73–88(in Spanish)
Goble RJ (1981) The leaching of copper from anilite andthe production of a metastable copper sulfide structure.
Canad Mineral 19: 583–591
Gordillo CE, Lencinas A (1979) Pampean Ranges of
Córdoba and San Luis. In: Turner JC (ed) 2º Simposiode Geología Regional Argentina. Academia Nacional deCiencias, Córdoba 1: 577–646 (in Spanish)
Hatert F (2005) Transformation sequences of copper
sulfides at Vielsam, Stavelot Massif, Belgium. CanadMineral 43: 623–635
314

Hauy R (1798) Sur la dioptase. Bul Sci Soc Phil 2: 101
Kay SM, Ramos VA (1996) The Cretaceous magmatism of
the Sierra de Córdoba and its tectonic implications. In:
Proceedings of the 13º Congreso Geológico Argentino,
Buenos Aires, 3: 453–464 (in Spanish)
Kerrich B (1987) Stable isotope studies of fluids in thecrust. In: Kyser TK (ed) Short Course in Stable Isotope
Geochemistry of Low Temperature Fluids. Mineralogical
Association of Canada, Saskatoon, 13: 258–286
Kim S-T, O’Neil JR (1997) Equilibrium and nonequilibriumoxygen isotope effects in synthetic carbonates. Geochim
Cosmochim Acta 61: 3461–3475
Le Bail A, Duroy H, Fourquet JL (1988) Ab-initio structure
determination of LiSbWO6 by X-ray powder diffraction.
Mater Res Bull 23: 447–452
Lira R, Ocanto C, Ripley EM (2008) Hydrogen and oxygenisotope data of epidote-group minerals: evidence for theorigin of some metasomatic and deuteric-hydrothermal
fluids from the Sierras Pampeanas of Córdoba, Argentina.
In: Linares E, Cabaleri NG, Do Campo MD, Ducós
EI, Panarello HO (eds) Proceedings of the VI SouthAmerican Symposium on Isotope Geology. San Carlos
de Bariloche (CD-ROM)
Luque FJ, Pasteris JD, Wopenka B, Rodas M, Barrenechea
JF (1998) Natural fluid-deposited graphite: mineralogicalcharacteristics and mechanisms of formation. Am J Sci
298: 471–498
Markham NL (1959) Occurrence of jordanite in the Otavi
Mountains, South West Africa. Amer Miner 44: 682–685
Mishra B, Pal N (2008) Metamorphism, fluid flux, andfluid evolution relative to gold mineralization in the
Hutti–Maski Greenstone Belt, Eastern Dharwar Craton,
India. Econ Geol 103: 801–827
Moritz R (2006) Fluid salinities obtained by infrared microthermometry of opaque minerals: implications forore deposit modeling – a note of caution. J Geochem
Explor 89: 284–287
Mutti D, Di Marco A (1999) Copper–iron and lead–zinc
deposits related to submarine volcanism, Córdoba. In:
Zappettini EO (ed) Recursos Minerales de la República
Argentina. Instituto de Geología y Recursos Minerales,
SEGEMAR, Buenos Aires, Anals 35: 207–225 (in Spanish)
Mutti D, Di Marco A, Fernández S (1998) Ore deposits in
the Neoproterozoic back-arc system of the central–south
Sierras de Córdoba, Argentina. In: Proceedings of the
6º Congreso Nacional de Geología Económica, Buenos
Aires 3: pp 81–87
Naden J, Shepherd TJ (1989) Role of methane and carbon
dioxide in gold deposition. Nature 342: 7936–795
Newberg DW (1967) Geochemical implications of chrysocolla-bearing alluvial gravels. Econ Geol 62: 932–956
O’Neil JR, Clayton RN, Mayeda TK (1969) Oxygen isotope fractionation in divalent metal carbonates. J Chem
Phys 51: 5547–5558

Copper mineralization in marble, Córdoba, Argentina

Ohmoto H, Rye RO (1979) Isotopes of sulfur and carbon.
In: Barnes HL (ed) Geochemistry of Hydrothermal
Deposits, 2nd edition. John Wiley and Sons, New York,
pp 509–567
Olsacher J (1938) The minerals from the Córdoba Ranges.
Imprenta de la Universidad Nacional de Córdoba, Córdoba, pp 1–71 (in Spanish)
Panarello HO, García CM, Valencia SA, Linares E (1980)
Determination of the isotopic composition of carbon, its
use in hydrogeology and geology. Rev Asoc Geol Arg
35: 460–466 (in Spanish)Pauliš P, Škoda R, Novák F (2006) Dioptase from uranium
deposit Zálesí in Rychlebské hory Mts. (Czech Republic).
Čas Slez Muz Opava (A) 55: 77–79 (in Czech)
Pirajno F (1992) Hydrothermal Mineral Deposits: Principles
and Fundamental Concepts for the Exploration Geologist.
Springer Verlag, Berlin, pp 1–709
Poklepovic MF, Colombo F, Lira R (2001) Microthermometric data on dioptase from Esperanza quarry, Sierras
Chicas, Córdoba, Argentina. Abstract. In: Noronha F,
Dória A, Guedes A (eds) XVI European Current Research
On Fluid Inclusions. Faculdade de Ciências do Porto,
Departamento de Geologia, Memória nº 7: 373–374
Pouchou J-L, Pichoir F (1985) “PAP” (ϕρZ) procedure for
improved quantitative microanalysis. In: Armstrong
JT (ed) Microbeam Analysis. San Francisco Press, San
Francisco, pp 104–106
Pudack, C, Halter, WE, Heinrich, CA, Pettke, T (2009)
Evolution of magmatic vapor to gold-rich epithermal liquid: the porphyry to epithermal transition at Nevados deFamatina, northwest Argentina. Econ Geol 104: 449–477
Rapela CW, Pankhurst RJ, Casquet C, Baldo E, Saavedra
J, Galindo C, Fanning CM (1998) The Pampean Orogeny of the southern proto-Andes: Cambrian continental
collision in the Sierras de Córdoba. In: Pankhurst RJ,
Rapela CW (eds) The Proto-Andean Margin of Gondwana. Geological Society London Special Publications
142: 181–217
R apela CW, B aldo EG, P ankhurst R, F anning CM(2008) The Devonian Achala Batholith of the Sierras Pampeanas: F-rich, aluminous A-type granites.
In: Linares E, Cabaleri NG, Do Campo MD, Ducós
EI, Panarello HO (eds) Proceedings of the VI SouthAmerican Symposium on Isotope Geology. San Carlos
de Bariloche (CD-ROM)
Richards JP, Spooner ETC (1989) Evidence for Cu–(Ag)mineralization by magmatic–meteoric fluid mixing in
Keweenawan fissure veins, Mamainse Point, Ontario.
Econ Geol 84: 360–385
Roisnel T, Rodríguez-Carvajal J (2001) WinPLOTR: aWindows tool for powder diffraction pattern analysis.
In: Delhez R, Mittemeijer EJ (eds) Materials Science
Forum, Proceedings of the Seventh European Powder
Diffraction Conference (EPDIC 7, Barcelona), 118–123

Rosenbaum J, Sheppard SMF (1986) An isotopic study ofsiderites, dolomites, and ankerites at high temperatures.
Geochim Cosmochim Acta 50: 1147–1150
Rusk BG, Reed MH (2008) Fluid inclusion evidence formagmatic–hydrothermal fluid evolution in the porphyry
copper–molybdenum deposit at Butte, Montana. Econ
Geol 103: 307–334
Russell B, Jens G, Harald S, Eva S, Craig M (2010) Sulfur
isotope characteristics of metamorphosed Zn–Cu volcanogenic massive sulfides in the Areachap Group, Northern
Cape Province, South Africa. Miner Depos 45: 481–496
Rye RO, Ohmoto H (1974) Sulfur and carbon isotopes andore genesis: a review. Econ Geol 69: 826–842
Sato M (1960) Oxidation of sulfide ore bodies. 1. Geochemical environments in terms of Eh and pH. Econ
Geol 55: 928–961
Seal II RR (2006) Sulfur Isotope Geochemistry of Sulfide
Minerals. In: Vaughan DJ (ed) Sulfide Mineralogy andGeochemistry. Mineralogical Society of America andGeochemical Society Reviews in Mineralogy and Geochemistry 61: 633–677
Seal II RR, Rye RO (1993) Stable isotope study of fluidinclusions in fluorite from Idaho: implications for continental climates during the Eocene. Geology 21: 219–222
Sfragulla J, Jerez D, Bonalumi A (1999) Marbles and othercarbonate rocks from Córdoba. In: Zappettini EO (ed)Recursos Minerales de la República Argentina. Institutode Geología y Recursos Minerales SEGEMAR, Buenos
Aires, Anals 35: 271–295 (in Spanish)
Sillitoe RH (2010) Porphyry copper systems. Econ Geol
105: 3–41
Turchyn AV, Schrag DP, Coccioni R, Montanari A (2009)
Stable isotope analysis of the Cretaceous sulfur cycle.
Earth Planet Sci Lett 285: 115–123
Vochten R, Janssens J, Blaton N (2005) Reinvestigation of
dioptase–planchéite pseudomorphs after calcite from theTantara copper deposit, Katanga, Republique du Congo.
Miner Rec 36: 521–524
Walstrom RE (2006) Chasing the green goddess: dioptase
in New Mexico. New Mex Geol 28: 110
Whitney DL, Evans BW (2010) Abbreviations for names ofrock-forming minerals. Amer Miner 95: 185–187
Williams SA (1962) Paramelaconite and associated minerals
from the Algomah Mine, Ontonagon County, Michigan.
Amer Miner 47: 778–779
Witt WK, Knight JT, Mikucki EJ (1997) A synmetamorphic
lateral fluid flow model for gold mineralization in theArchean southern Kalgoorlie and Norseman terranes,
Western Australia. Econ Geol 92: 407–437
Yates DM, Joyce KJ, Heaney PJ (1998) Complexation ofcopper with polymeric silica in aqueous solution. Appl
Geochem 13: 235–241
Zhang X, Nesbitt BE, Muehlenbachs K (1989) Goldmineralization in the Okanagan Valley, southern British
315

Fernando Colombo, Raúl Lira, Edward M. Ripley, José González del TánagoColumbia: fluid inclusion and stable isotope studies.
Econ Geol 84: 410–424

316

Zheng YF (1999) Oxygen isotope fractionation in carbonate
and sulphate minerals. Geochem J 33: 109–126